1. Field of the Invention
The invention relates to a polyamine epoxide adduct, useful, e.g., as a component in a polyurea coating formulation.
2. Background of the Invention
Sprayable polyurea elastomers are widely used as coating materials on various substrates such as metals, plastics, wood and concrete. Sprayable formulations of polyurea have the advantage of setting rapidly. Conventional polyurea sprays do not perform well in some environments, exhibiting poor elastomeric properties and poor chemical resistance when exposed to conditions of high acidity, or the presence of hydrocarbons such as xylene or toluene. Prior attempts to apply polyurea coatings to substrates in such environments have included using epoxy resins as primers, but unfortunately expoxy resins cure slowly and present bad odors.
It is thus an object of the invention to provide a polyurea polymer which exhibits good adhesive properties and chemical resistance, while preserving optimal set rates and flowability.
The invention features a polyamine epoxide adduct, characterized in that an epoxy group is added to the terminal amino groups of a polyamine. The polyamine epoxide adduct is prepared by admixing a source of epoxy group with a polyamine, and allowing the epoxy groups to react with the terminal amino groups of the polyamine so as to form the polyamine epoxy adduct. The terminal amino groups react with the epoxy ring to form an amine-alcohol linkage, or adduct.
The polyamine epoxide adduct of the invention can be used, e.g., as a component for preparing a polyurea polymer, thereby providing the resulting polyurea polymer with improved properties of adhesiveness and chemical resistance. Polyurea polymers prepared from polyamine epoxide adducts demonstrate better resistance to acid and to hydrocarbons, e.g., aromatic hydrocarbons, e.g., xylene and toluene. Furthermore, polyurea polymers prepared from polyamine epoxide adducts of the invention demonstrate improved adhesion to substrates than do conventionally prepared polyurea formulations, when applied alone or in the presence of an epoxy resin primer. Thus, polyurea polymer formulations of the invention are advantageously used as coating on substrates such as, without limitation, metal, steel, wood, plastic, and concrete.
Accordingly, in one aspect the invention features a polyamine epoxide adduct useful in preparing a polyurea polymer which has increased chemical resistance to, e.g., acids and hydrocarbons, and has improved adhesive properties for adhering to, for example, a substrate, e.g., a concrete, metal, e.g., steel, wood, or plastic substrate. Preferably, the polyamine is present in stoichiometric excess relative to the concentration of epoxy groups, so that the epoxy groups are reacted fully on the backbone of the polyamine.
The invention further features a method of preparing a polyamine epoxide adduct by admixing an epoxy group that is able to react with a terminal primary amine along with a polyamine hardener, under conditions in which the epoxy group is added to the amino-terminal ends of the polyamine backbone. Preferably, the concentration of polyamine stoichiometrically exceeds that of the epoxy groups, so that the epoxy groups are substantially consumed when reacting with the polyamine. Alternatively, or in addition, the method can include the further, optional, step of removing any remaining epoxy groups from the prepared polyamine epoxide adduct. Excess epoxy groups can be removed by methods known to those skilled in the art, such as, e.g., by vacuum.
Without limitation, the polyamine epoxide adduct of the invention can be used as a component for preparing a polyurea polymer, thereby providing the resulting polyurea polymer with improved properties of adhesiveness and of chemical resistance. The polyamine epoxide adduct is substituted for the polyamine in a conventional method of preparing a polyurea by mixing a polyamine with a polyisocyanate, preferably in the presence of an optional chain extender. Optionally, where the chain extender is itself a polyamine, the polyamine epoxide adduct can be used as a substitute for the chain extender. The polyamine epoxide adduct prepared by the method of the invention is substantially free of unincorporated epoxy groups, so there is no substantial level of epoxy groups present in the reaction mixture when forming the polyurea.
Accordingly, the invention further features a polyurea polymer formulation that includes a polyamine epoxide adduct, and a method of preparing a polyurea polymer formulation that is based on a polyamine epoxide adduct component. The method includes the steps of allowing a polyamine epoxide adduct to react with a polyisocyanate, under conditions suitable for forming a polyurea polymer.
In a related aspect, the invention features an apparatus that includes a substrate, block, or surface coated with a polymer coating based at least in part on a polyurea prepared from a polyamine epoxide adduct. Suitable substrates and surfaces are composed at least in part of, e.g., metal, steel, wood, plastic, or concrete. The invention also features a method for applying a polyurea polymer coating to a substrate or surface thereof, the method including the step of applying a polyurea polymer coating prepared from a polyamine epoxide adduct to the substrate.